Curvature and confinement effects on chiral liquid crystal morphologies

Chiral liquid crystals (ChLCs) exhibit an inherent twist that originates at the molecular scale and can extend over multiple length scales when unconstrained. Under confinement, the twist is thwarted, leading to formation of defects in the molecular order that offer distinct optical responses and op...

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Bibliographic Details
Published in:Soft matter 2023-08, Vol.19 (32), p.666-673
Main Authors: Palacio-Betancur, Viviana, Armas-Pérez, Julio C, Hernández-Ortiz, Juan P, de Pablo, Juan J
Format: Article
Language:English
Subjects:
Assembly
Confinement
Crystal defects
Crystal morphology
Crystals
Curvature
Free energy
Hypothetical particles
Liquid crystals
MATERIALS SCIENCE
Particle theory
Phase diagrams
Ribbons
Surface defects
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Summary:Chiral liquid crystals (ChLCs) exhibit an inherent twist that originates at the molecular scale and can extend over multiple length scales when unconstrained. Under confinement, the twist is thwarted, leading to formation of defects in the molecular order that offer distinct optical responses and opportunities for colloidal driven assembly. Past studies have explored spheroidal confinement down to the nanoscopic regime, where curved boundaries produce surface defects to accommodate topological constraints and restrict the propagation of cuboidal defect networks. Similarly, strict confinement in channels and shells has been shown to give rise to escaped configurations and skyrmions. However, little is known about the role of extrinsic curvature in the development of cholesteric textures and Blue Phases (BP). In this paper, we examine the palette of morphologies that arises when ChLCs are confined in toroidal and cylindrical cavities. The equilibrium morphologies are obtained following an annealing strategy of a Landau-de Gennes free energy functional. Three dimensionless groups are identified to build phase diagrams: the natural twist, the ratio of elastic energies, and the circumscription of a BP cell. Curvature is shown to introduce helical features that are first observed as a Double Twist, and progress to Chiral Ribbons and, ultimately, Helical BP and BP. Chiral ribbons are examined as useful candidates for driven assembly given their tunability and robustness. Simulations of chiral LCs under toroidal confinement explore the free energy landscape of forming new morphologies that can be tuned through material properties and confinement geometry.
ISSN:1744-683X
1744-6848
DOI:10.1039/d3sm00437f